Process of dewaxing oils



Mardi 5', 1940. R K STRATFQRD E1- AL I 2,192,718

PRocEss 0F DEWAXING oILs Filed Nov. l, 1954 UNDEw/Itxfr) L V HI. R l 3, E u E 5 R Y D G a f a e 2 m m myn a ,d m ...M m y m u M` mf1, E VP. W E ab T l .r M g a a m am 5% l a :f Ilya WH; lW 4 L www Mm o0 7 H www ou M w www Q2u J Q J 5 f M n 1 Il' r11-,l1 T 0 ,nw G r, Il' A .^v. 1 N L w .wk mm 3 wwwmluwm a 1W w T, n E c s N M R vs WAv sm w75 E E RG ,3 s Y H 0 LM H en. I.' l'. C R.. @wm Le E u Ix i., 2 wd N f Lf Aff, op 7J .n l f 5 WAK ,N Il 3R... R fx A m B 2 l LS I MSM/m o Patented Mar. 5, 1940 UNITED sTATEs PATENT OFFICE rRooEss or DEWAXING olLs Delaware Application November 1, 1934, Serial No. 750,937

5 Claims.

This invention relates to a process of dewaxing petroleum oils such as residual cylinder stocks, overhead lubricating stock, distillates, etc. and Will be fully understood from the following description when read in conjunction with the drawing, the sole figure of which is a diagrammatic side elevation partly in section of an apparatus appropriate for carrying out the invention.

According to the present invention the dewaxing is carried out by means of a liquid dewaxing mixture containing a selective solvent which is used as a precipitant for the wax, and an inert solvent for oils. The properties of the selective Y, solvent and the inert solvent to be used according to the present invention will be described in the following.

A considerable number of so-called selective solvents have been used recently for treating oils, such as gasolines, kerosenes, lubricating oils, etc.

A true selective solvent is characterized by the capability of extracting compounds of a certain chemical structure from a mixture of said compounds with compounds of different chemical structure, as ina hydrocarbon oil. W'e have discovered that selective solvents having a selectivity for unsaturated and aromatic hydrocarbons and having a boiling point higher than about 150 F. can be successfully used as precipitants for wax in a dewaxing mixture, the other component being an inert solvent. The following examples of selective solvents to be used in our invention are mentioned: ortho-, meta, and para-cresol, ethers of phenol, such as those found in creosote oil. The preferred selective solvents used in our invention are those which have a boiling point above 200 F. or above 300 F.

The inert oil solvent used in the present invention is preferably a light oil of unsaturated, naphthenic, or aromatic character, such as a gasoline or kerosene extract obtained by extracting a gasoline or a kerosene stock with a selective solvent, such as triphenyl phosphate, tricresyl phosphate, liquid sulfur dioxide, aniline, etc., aromatic hydrocarbons which have a moleculai1 weight equal to or higher than toluene, such as toluene, xylene, hydrogenated naphthalenes, such as: Tetralin; hydrogenated aromatic hydrocarbons, naphthenic hydrocarbons, such as: cyclohexene; aliphatic ethers, such as: isopropyl ether, heat stable chlorinated aromatic hydrocarbons, such as orthodichlorbenzene.

The liquid dewaxing mixture consisting of the selective solvent and the inert solvent must have the property of low miscibility point with the dewaxing oil in order to prevent the separation of two liquid phases during the dewaxing process. This miscibility temperature should be less than about 25 F. and preferably less than 35 F. It is determined by dewaxing rst the oil by any method known to the art and then determining 5 the miscibility point by cooling down a mixture of the oil and the dewaxing agent to low temperature in the dilution in Awhich the dewaxing agent is to be used during the dewaxing process. The temperature at which formation of a heavy cloud 10 appears indicates the separation of two liquid phases and is taken as the miscibility temperature.

The composition of the dewaxing mixture is, to a large extent, determined by the miscibility point 15 of the mixture with the dewaxed oil. With most selective solvents it is necessary to have a proportion of at least 50% by volume and preferably around 65-75% by volume of the inert solvent in the dewaxing mixture. with selective 20 solvents, however, which have a low miscibility temperature with the dewaxed oil, smaller amounts of the inert solvent in the dewaxing mixture will be suicient.

The proportion of the dewaxing mixture and 25 the oil to be dewaxed depends largely on the viscosity of the oil. Two volumes of dewaxing mixture to one volume of the oil usually give good results with less viscous oils, but with higher viscosity oils such as cylinder stocks, it becomes necessary to increase the ratio of the dewaxing mixture to the oil to 4:1.

In carrying out the process the dewaxing mixture is admixed with the oil and then the mixture is cooled down to a temperature at which the precipitation of the wax takes place. This temperature will depend on the desired pour point of the dewaxed oil and is usually 5-20 F. below the pourpoint. Thus, for example, if it is required to obtain a lubricating oil of |5 F. 40 pour point, it will be necessary to cool the mixture of oil and dewaxing agent to around 5 F.

The invention is not to be restricted to the above method of solvent dewaxing. It is often found advantageous to dissolve the undewaxed oil in one to ltwo volumes of the dewaxing solvent mixture and obtain the required dilution by adding the cold solvent mixture used for washing the slack wax cake. By this process, the yield of' dewaxed oil is increased from 5.0 to 10.0% 50 and a wax practically free from oil is obtained as a lay-product.

The separation of the precipitated Wax from thedewaxing mixture may beV carried out by any of the usual methods, such as by cold settling,

filter pressing, centrifuging, etc. After the separation of the Wax, the dewaxing mixture is removed from the oil by means of distillation or any other means.

Referring now to the sole gure of the drawing, the same will be described in conjunction with the method of operating the apparatus. Undewaxed lubricating oil stock from storage tank I and dewaxing mixture from storage tank 2 are passed by means of pumps 3 and 4 and mixing pump 5 or other mixing device through the heat exchanger 6 and brine chiller 1 into the rotary filter 8 or other means for separating Wax from oil, such as lter press or settling tank, etc.

' The pressed oil dissolved in the dewaxing mixture is removed from the filterl through line 9 and heat exchanger 6 into the storage tank I0. The screw conveyor II forwards the slack wax into the tank l2, from which latter it is passed by means of pipe I3 through heat exchanger III and heater i5 into the stripping tower I6, which may be provided with baie -plates (not shown). In the heater I5 the slack wax is heated to a high enough temperature to remove substantially all the dewaxing mixture which it contains. This mixture passes as vapor to overhead line I'I, is condensed in condenser I8 and collected in rundown tank it, from which it is returned by means of pump 2li, lines 2l and 23, into the dewaxing mixture storagey tank 2. The hot slack wax is removed from the bottom of stripping tower IIS through line 2li and heat exchanger I4 into slack wax storage tank 25. From this storage tank the slack wax may from time to time be transferred through line 2li to sweaters and wax finishing plant. The solution of pressed oil in the dewaxing mixture is taken from storage tank I0, pumped by 2l through line 28, heat exchanger 29 and heater 30 into a rst stripping tower 3I. The dewa-xing mixture is removed in this' tower by the overhead line 32, condensed in 33, and collected in rundown tank 34, from which it is pumped by 35 through lines 22 and 23 into the dewaxing mixture storage tank 2.. The bottoms from tower 3l consisting of substantially solvent free dewaxed oil is pumped by 36 through line 31, heat exchanger 29 and cooler 38 into the pressed oil storage tank 39. If so desired a second stripping tower may be provided into which the bottoms from tower 3l is discharged, either with or without further heating. Vacuum may be applied on the second tower or steam may be used in certain cases to eiect further stripping of the oil.

The following examples will illustrate our invention:

1. One part by volume of phenol treated Mid- Continent cylinder stock is dissolved in three to four parts by volume of a solvent composed of a mixture of 65% by volume of SO2 extract from refined oil, boiling within the approximate range of 300 to 456 F., and 35% of cresol. The wax is precipitated from the solution by chilling to a temperature of approximately 5 to 10 degrees below the pour test desired in the dewaxed oil, and then filtered. The filtrate is distilled in order to strip the solvents from the dewaxed pressed oil bottoms. In another stripping unit the solvent is recovered from the slack wax cake. The yield of recovered dewaxed oil depends on the stocks i ume of beta-beta-dichlorethyl ether.

and to some extent on the method of ltration. It is about 65% or better.

2. Similar results are obtained by replacing the cresol in. the dewaxing mixture with 35% by vol- The yield of recovered pressed oil is approximately 66% with a pour point about 5 F. above the ltration temperature.

3. Carrying out the experiment as in Example 1, but replacing the cresol with 35% of nitrobenzene, the wax is precipitated by chilling to between +5 and 0 F., that is, above the crystallization point of nitrobenzene, and separating the oil in solution from the wax by forcing the chilled mixture through a filter press. A yield of about 72% of pressed oil having a pour point between 20 and 25 F. is obtained.

4. One part by volume of phenol treated Mid- Continent cylinder stock is dissolved in three to four volumes of a solvent composed of a mixture of approximately 25% of SO2 extract from rened oil (boiling range 30D-450 F.) and 75% of ethylene dichloride. The wax is precipitated from the solution by chilling to a temperature of approximately the pour test desired in the dewaxed oil and then ltered. The recovery of the dewaxing solvent mixture is illustrated in the drawing. A 65% yield of pressed oil is obtained having the same pour point as the temperature to which the solution was chilled.

5. As an example of the use of aromatic and hydro-aromatic inert solvents or diluents, the use of toluene may be given:

One part by volume of phenol treated Mid- Continent cylinder stock is dissolved in three to four volumes of a dewaxing solvent composed of a mixture of approximately 65% of toluene and 35% of cresol (boiling range 380-397.5 F.) or beta-beta-dichlorethyl ether. After chilling to a temperature about 5 F. belowfthe desired pour point, the separated Wax is removed by means of a filtration and the dewaxing solvent stripped from the pressed oil and slack wax as described above. 'I'he yield approximates 66% on charge.

6. The use of chlorinated aromatic hydrocarbons as inert solvents or diluents is illustrated by the following example:

One part by volume of phenol treated mel-Continent cylinder stock is dissolved in three to four volumes of a solvent composed of 65% of orthodichlorbenzene and 35% of cresol or beta-betadichlorethyl other (chlorex). The chilled mixture then either forced through a filter or centrifuged to separate the precipitated wax from the solution of oils. The dewaxing solvent l .ixture is recovered from the nitrate and slack cake by distillation. Yields of 64 to 56% of dewaxed oil are obtained, the pour point being 5 to F. above the chilling temperature.

In some cases it is desirable to have more than one selective and/or inert solvent in the dewaxing mixture in order to properly control the process. Our invention may be modified in various other Ways; therefore, it is not to be limited by the examples given for ilhstn ion but only by the following claims in which. it is our intention to claim all novelty inherent in the invention.

What we claim is:

l. The process of dewaxing a wax containing oil which comprises admixing with the oil a liquid dewaxing mixture which a miscibility temperature of less lthan about 25 F. with the dewaxed oil, said liquid dewaxing mixture consisting of a selective solvent of phenolic structure having a selectivity for aromatic hydrocarbons and having a boiling point higher than about 150 F., and an inert oil solvent which belongs to the class consisting of a light petroleum oil of unsaturated, naphthenic or aromatic character obtained as extract in the extraction of a light petroleum distillate with a selective solvent, aromatic hydrocarbons having a molecular weight equal to or higher than toluene, hydrogenated aromatic hydrocarbons and naphthenic hydrocarbons, and heat stable chlorinated aromatic hydrocarbons, cooling the mixture of oil and devvaxing mixture to a low temperature at which the Wax precipitates out, separating the precipitated Wax, and removing the dewaxing mixture from the oil.

2.l The process of dewaxing a Wax containing oil which comprises admixing with the oil a liquid dewaxing mixture which has a miscibility temperature of less than about F. with the devvaxed oil, said liquid deWaxing mixture consisting of a selective solvent of phenolic structure having a selectivity for aromatic hydrocarbons and having a boiling point higher than about 150 F., and an inert oil solvent which consists of a light petroleum distillate of unsaturated, naphthenic, or aromatic character obtained as extract in the treatment of a light petroleum distillate with a selective solvent of the type of phosphate of a phenol, liquid sulfur dioxide, aniline, furfural, cooling the mixture of oil and dewaxing mixture to a low temperature at which the Wax precipitates out, separating the precipitated Wax, and removing the dewaxing mixture from the oil.

3. Process of dewaxing a wax containing oil which comprises admixing with the oil a liquid dewaxing mixture containing a cresol and toluene, cooling the mixture of oil and dewaxing mixture to a low temperature at which the Wax precipitates out, separating theprecipitated Wax, and removing the dewaxing mixture from the oil.

4. Process of dewaxing a Wax-containing oil which comprises admixing the oil with a liquid dewaxing mixture having a miscibility temperature with the oil of less than 25 F., said liquid mixture consisting of between 25 and 35% of a selective solvent of phenolic structure having a boiling point above 150 F. and between 75 and 65% of a selective solvent extract of a hydrocarbon oil boiling Within the approximate range of D-450 F., cooling the mixture to a temperature at which wax is caused to precipitate, removing the Wax and recovering dewaxed oil.

5. Process of dewaxing a wax-containing oil which comprises admixing the oil with a liquid dewaxing mixture consisting of about cresol and about of a selective solvent extract of a refined hydrocarbon distillate boiling between 300 and 450 F., cooling the mixture of oil and dewaxing mixture to a temperature at which wax is caused to precipitate, removing the wax and recovering dewaxed oil.

REGINALD K. STRATFORD. OLDRICI-I S. POKORN'Y. 

